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When I ask people working in CX which metric they use to measure customer experience, I usually get a one-word answer: NPS. And when I ask why NPS specifically, I often hear something along the lines of “because everyone measures it.” That’s the kind of answer that makes me, as an analyst, a little uneasy. Not because NPS is a bad metric. But because “everyone measures it” isn’t a reason. It’s a habit.
I’ll admit I did the same thing for a long time. For years I saw Customer Effort Score (CES) as the younger sibling of NPS something useful, but not “the” main metric. It took me a few years and several research projects to realise that CES and NPS don’t measure the same thing from a different angle. They measure entirely different things. And if you only use one of them, you’re looking at your customer with one eye closed.
What each metric actually measures
Let’s start with the basic difference, because it often gets blurred in practice.
NPS is by now a classic. Fred Reichheld introduced it in 2003 in a piece that has since become almost required reading in the CX world: “The One Number You Need to Grow” in the Harvard Business Review. The principle is simple: you ask the customer how likely they are to recommend your company to a colleague or friend. You sort the answers on a 0–10 scale into three groups (promoters 9–10, passives 7–8, detractors 0–6), and the result is the difference between the percentage of promoters and detractors. Reichheld argued at the time that this single question correlated with company growth better than any other. And because it sounded compelling, people believed it.
CES came along seven years later with a far more provocative ambition. In 2010, Matthew Dixon, Karen Freeman and Nicholas Toman published an article in the Harvard Business Review with the manifesto-like title “Stop Trying to Delight Your Customers.” It was based on a large study by the Corporate Executive Board (now part of Gartner) covering more than 75,000 customers, and its main finding was uncomfortable: trying to “wow” customers has surprisingly little effect on loyalty. What actually predicts loyalty is something far more mundane how easy it is to do business with the company. That finding gave rise to the question CES still uses today: “To what extent do you agree that the company made it easy for you to handle your issue?” Responses are recorded on a 1–7 scale.
Here’s the crucial difference that’s easy to miss: NPS measures the relationship, CES measures the interaction. NPS asks what the customer thinks about the company as a whole. CES asks how smoothly a specific thing they were dealing with went.
It sounds like a small nuance. But in practice it means that if you only measure NPS, you don’t know where exactly your customer journey is grinding. And if you only measure CES, you don’t know whether your customers actually like you.
Why effort beats delight, surprisingly
This is one of the things I really enjoy about CX: sometimes the data tells you something completely different from what you’d expect. Look at the original research that gave rise to CES, and you get a rather alarming picture. Customers who had a “high-effort” interaction with a company became less loyal in 96% of cases. For low-effort interactions, that figure was just 9%. In other words, a bad experience costs you loyalty far faster than a good experience earns it.
This asymmetry has a deep psychological foundation. Daniel Kahneman and Amos Tversky described it back in 1979 in their prospect theory: losses hurt roughly twice as much as equivalent gains feel good. When a customer has to be transferred between four agents to fix a billing error, they don’t walk away thrilled that it was eventually resolved. They walk away annoyed that it took so long.
In its follow-up studies, Gartner went further and compared the predictive power of individual metrics. According to its research, CES predicts future customer behaviour contract renewal, repeat purchases, increased spend about 12 percentage points more accurately than satisfaction, and nearly twice as accurately as NPS. But only in the context of service interactions. That’s an important caveat I’ll come back to in a moment.
When to use which
If I were to sum up what I’ve learned over the years working with these metrics, it would look something like this:
NPS makes sense when you want to know how strong your relationship with the customer is. It suits relational measurement not after every interaction, but at regular intervals, typically quarterly or every six months. It works well in contexts where the customer has a long-term relationship with the company and where asking about an overall impression actually makes sense: telecoms, banks, B2B services, software as a service. NPS is a useful strategic metric for leadership a single aggregated indicator you can track over time and (with great care) compare with competitors.
CES makes sense when you want to know whether a specific moment in the customer journey is working. It suits transactional measurement immediately after a particular interaction. After a complaint has been resolved. After an order has been placed. After a call with support. After onboarding. CES is an operational metric that tells you exactly where the customer is struggling. And because it’s tied to a specific event, you can act on it straight away: improve a particular step, retrain a particular team, redesign a particular form.
Think of it this way: NPS is like an annual check-up at the doctor that tells you how you’re doing overall. CES is like a blood pressure monitor you reach for whenever you suspect something might be wrong. You need both. But you need them at different moments and for different decisions.
Why companies end up using only one
When I talk to people at companies that only measure NPS, I usually hear two arguments. The first is simplicity: “one number that leadership understands.” The second is tradition: “we’ve been measuring it for five years, we have a time series.” I understand both. But both have a catch.
One number that leadership understands is a lovely thing, but NPS on its own doesn’t tell you what to do. If it drops from 42 to 38, that’s bad. But why? Where? In which part of the customer journey? NPS won’t answer that. So companies often add an open-ended “Why?” question alongside NPS and then drown in hundreds of unstructured responses that are hard to turn into an action plan.
And a time series is only useful if the metric measures what you actually need to manage. If you’re an e-commerce company trying to improve cart conversion, NPS won’t help much. CES after a completed (or abandoned) order will.
It’s worth noting that even Bain & Company, the firm behind the creation of NPS, recommends in its own materials a combination of relational and transactional measurement essentially NPS combined with something else, whether CES or CSAT (Customer Satisfaction Score). NPS was never meant to be the only metric. It became one because it’s so catchy.
How to combine them meaningfully
Here’s the thing I enjoy most about CX: the best results usually don’t come from picking the “right” metric, but from building a sensible system.
In practice, it pays to split measurement into two layers. Relational NPS is measured at regular intervals (quarterly, every six months) across the whole customer base and serves as a strategic indicator for leadership. You watch the trend, segment by customer type, and correlate it with real behaviour contract renewals, churn, growth in spend.
Transactional CES is measured continuously after key interactions the ones you’ve identified as moments of truth in your customer journey. After a support ticket is resolved. After onboarding is finished. After a first purchase. Here CES acts as an operational signal that lets you quickly spot where the customer is struggling and do something about it immediately.
These two layers inform each other. When relational NPS drops, you look at recent transactional CES data to find the source. When transactional CES flags a problem at a specific step in the journey, you watch to see whether it eventually shows up in relational NPS.
Forrester recommends something similar. In one of its reports on the state of CX measurement, it notes that companies combining multiple types of feedback relational, transactional and behavioural are significantly more likely to translate improvements in customer experience into measurable business results. A single metric, however good, won’t give you that connected picture.
So what now
If you’re a company that currently only measures NPS, I don’t think it’s a fatal mistake. NPS has its value, and there’s no point in abandoning it. But it’s worth asking whether that one metric is really enough to tell you where in the customer journey you need to act. If you find that you can’t give a concrete answer to “why has our NPS dropped” over and over again, that’s a signal you’re missing the transactional layer of measurement.
And if you’re a company that only measures CES (which is rarer, but it happens, particularly with product-led tech companies), try asking yourself whether you actually know how strong your relationship with the customer is outside of specific interactions. A product being easy to use doesn’t mean the customer will recommend you. Sometimes they’ve just learned how to use it, and the first competitor’s offer will convince them they can get the same ease elsewhere.
The thing that’s been confirmed for me most over years of working with CX metrics is this: metrics are not the goal. They’re lenses through which we look at the customer. And one lens will never show you the whole picture. So the question isn’t “CES or NPS.” The question is: “What system of perspectives on the customer will give me answers I can actually act on?”
That’s the question I find fascinating. And I think it deserves far more attention than the endlessly recycled debates about whether NPS is dead or not.
